1. Field of the Invention
The invention relates to methods of production of mineral fibers, in which a stream of melted material falls onto the periphery of a rotor which has an approximately horizontal axis and which distributes the melted material to other rotors, the rotors forming the fibers by centrifuging. It relates in particular to the formation of mineral wools based on glass compositions or based on blast furnace slag or basalt, according to the methods described, in particular, in patent applications EP-A-0 167 508 or EP-A-0 059 152.
2. Description of the Related Art
In these methods, it is important to control the position of the point of impact of the stream of melted material on the first roller, and to do this not only in the tangential direction of the rotors where the position affects all the subsequent impacts on the following rotors, but also in the axial direction. Two phenomena depend on this latter position. In a stable process, the temperature of the rotors in the axial direction is not homogeneous since the melted material greatly heats the impact zone whereas the adjacent zones remain colder. It follows that an uncontrolled axial displacement of the zone cools the melted material--on each rotor--and alters the fiber-drawing conditions markedly and rapidly. It therefore is essential that displacements of this type are performed under the control of the operator of the machine.
Furthermore, periodic displacement of the impact zone has a certain advantage since it permits the wear of the surface of the rotor to be distributed over the entire length in the axial direction. It is essential to precisely know the axial position of the melted material for this purpose.
Methods of optical measurement of a stream of molten material which is falling onto a fiber-drawing machine are known. Some of them relate to the determination and the stabilization of the position of a stream of molten material intended to produce fibers by a direct blowing of the melted material. Observing the stream in question in the axial direction is possible in the process in question since the stream is sharply deflected and even disappears at the precise instant at which a burner, the axis of which is perpendicular thereto, produces the fibers.
In other methods, the stream of molten material on a fiber-drawing machine is observed by a CCD camera with the object of determining the width of the vertical stream, whereas radiation detectors are used to measure the velocity thereof. These two measures are performed with the object of calculating the flow rate of the material.
The person skilled in the art also knows of the use of CCD cameras to determine the position of objects and even, owing to mechanical, electrical and information systems, to control the relative position or relative displacement thereof. Opto-electronic observation systems have been developed specially for this purpose.